U.S. Patent Application Publication No. 2005/0217921 (hereinafter referred to as “US 2005/0217921 A1”) has the object of providing a driving force control method for four-wheel-drive vehicles. The control method is capable of adequately controlling the driving force distribution ratio for front and rear wheels, or the driving force distribution ratio for left and right front wheels or rear wheels ([0009], Abstract). According to US 2005/0217921 A1, in order to achieve this object, the driving force control method controls the driving force distribution ratio for the front and rear wheels in order to increase the driving force distribution ratio for the rear wheels, and also controls the driving force distribution ratio for the left and right front wheels or the rear wheels in order to increase the driving force for an outer wheel upon turning, depending on an increase in the absolute value of a lateral G signal. The lateral G signal is indicated by a control lateral G signal, which is generated by correcting a lateral G sensor signal with an estimated lateral G signal calculated on the basis of the vehicle speed and a steering angle of the vehicle (Abstract).
Japanese Laid-Open Patent Publication No. 2005-219580 (hereinafter referred to as “JP 2005-219580 A”) has the object of providing a vehicle behavior control apparatus, which is capable of suppressing a change in the behavior of a vehicle at the time that the vehicle starts to accelerate or decelerate while the vehicle is making a turn, thereby increasing vehicle stability ([0006], Abstract). In order to achieve this object, the behavior control apparatus 1 according to JP 2005-219580 A includes a drive means (electric motors 11FR through 11RL, [0024]) for applying individual driving forces respectively to a plurality of wheels 10FR through 10RL, a traveling state detecting means (lateral acceleration sensor 25, [0035]) for detecting a turning state of the vehicle V, and a driving force control means (motor ECU 20, [0032]) for controlling the drive means. The driving force control means controls the vehicle V so as to accelerate while the vehicle V is making a turn, and starts to apply a driving force to an outer wheel upon turning, and thereafter applies a driving force to an inner wheel during the turn (claim 3, [0052]).
With the behavior control apparatus 1 according to JP 2005-219580 A, when the vehicle V is accelerated while the vehicle is making a turn, a yaw moment is generated in the same direction as the direction of the turn, due to the fact that the driving force starts to be applied initially to the outer wheel during turning. It is claimed that a change in the behavior of the vehicle at the time that the vehicle starts to be accelerated can be suppressed, because the generated yaw moment cancels out a yaw moment that is generated in a direction opposite to the direction of the turn as the vehicle is accelerated ([0012]).
It is assessed whether or not the vehicle V is in a turning state on the basis of whether the lateral acceleration, which is detected by the lateral acceleration sensor 25, is equal to or greater than a predetermined value ([0034], [0035]).
According to JP 2005-219580 A, the driving force control means controls the drive means to start applying the driving force to the outer wheel upon turning, and thereafter applies the driving force to the inner wheel during the turn, provided that the absolute value of a rate of change of an accelerator pedal opening (rate of change |dAcc/dt|) is equal to or greater than a predetermined value TH1, and further provided that the absolute value of the difference between a preceding readout value of the accelerator pedal opening and a present readout value of the accelerator pedal opening (difference |ΔAcc|) is equal to or greater than a predetermined value TH2 (FIG. 3, step S106: YES) ([0037]). It further is stated that only one of these conditions, i.e., one of the rate of change |dAcc/dt| and the difference |ΔAcc|, may be used ([0037]).